What do you mean you can't see it? Or, indeed, can't see them? The species is Richardson's Case-bearer Eudarcia richardsoni​, a micro-moth known from just two localities in Britain (both on the Dorset coast) and, besides them, two distant locations in mainland Europe. That's pretty odd. Stranger still, this species shuns vegetation, inhabiting (in Dorset if not Switzerland!) the shattered scree-slopes of sea cliffs.

Adults are very hard to see, so the best way to survey the locations of this rarity are to search for... wait for it... its larval case, i.e. the structure encasing the pupa. In the case of a micro-moth, these can be very small indeed. But that didn't stop Mark and I having a go. Mark has been doing timed counts of larval cases around the Portland coastline for several years. Those surveys have been instrumental in making the case for Butterfly Conservation and other organisations to clear invasive cotoneaster which has been sprawling over Eudarcia​'s habitat. But what chance success? After about 20 minutes, we spotted two squidgy grains of rice covered in sand dust. In other words, the protective casing of one of the scarcest and strangest creatures living in Britain. Ladies and gentlemen, I give you... Richardson's Case-bearer.